Apparatus for rolling sheet metal



2 1953 'w. R. MACAULAY ET AL 2,660,077

APPARATUS FOR ROLLING SHEET METAL Filed Feb. 2, 1946 v 2 Sheets-Sheet 1 :0 N i 2 k 4 FIG. I

5'5) M Q INVENTORS O a WILLIAM R. MACAULAY a JOHN E. COOLIDGE IZM-A an... Ma... 13%...

1953 w. R. MACAULAY ET AL 2,660,077

APPARATUS FOR ROLLING SHEET METAL Fil ed Feb. 2; 1946 2 Sheets-Sheet 2 FIG. 2

0500000 ooucocoboooooooooococ 0000 o L 5 50 6 a 53 0 o 0 cm 0 a o o o a o o o o n o a la 0 0 7: o c o 0 INVEN'I'ORS WILLIAM R. MACAULAY 8 JOHN E. COOLIDGE LM-A ATTORNEYS Patented Nov. 24, i953 ztet'n UNITED. PATENT OF F'ICE 2;eeo,077 r APPARATUS FORROLLIN'GHSHEEIKMETAL.

Wil1iam Macaulay and' John E; Coolidge, Waterbury; Comp, assignors to- The-American BrassnCompany; a corporation of Connecticut Application Eeliruaryz, 1946, scrialNo. 645,204

(Cl;v 8 0-5'6?) 12 Claims.

orbar-of the metal and to" pass: it" repeatedly" through-'r'ollswhich are successively closer spaced: to .redu'ce-itstliickness to the.,final gauge'desired; The rolling: operation subjectsthe' metal to' severemechanical working, and it becomes increasingly workehardened with .successive passes through the rolls: Because of:this work hardening; it is necessary 'to. annealthe metalperiodicall'y'between successive series of passes through. i

the" rolls. For convenience in handlingthe'metalj. betweenrolli'ng' operations, it is coiled as it emerges from. the rolls; and it is; in the. coiled form that the. m'etalis' usually annealedj'inthe annealing; furnace. It. is. not alwayscommer cially feasible; to. conduct the. annealing. opera: tion: in such. manner; that, absolutely uniform. annealing of, themetal. throughout; the. coil; is achieved; Consequently, a: coil' of. metal after annealing is likely to, have. sections; that arerelatively less, well? annealed andv consequently relatively harder. thanothensectionsiin the same c.0111. These relatively, harder. sections; require;

greater. rolling: pressure to effect; a givenreduc:

tion'in: thickness. thanthesoiter sections; Cone.-

seoiuently, unless the rolling; pressure is. varied, during passage of. the annealedhstrip. through, the. rolls, so... as. tQincrease. the pressure while.- rolli'ngr the .harder sections. and to decrease. the. rolling; pressure: on the. softer, sections. a rolled. strip; of.uneven..thickn.ess willlbe produced. This unevenness. inv the.thickness. of. the: roll. is. par-- ticularly troublesome in producingsheet. Orstrip, ofthin. gauge, because in thinegauge metal, a

thickness; variation ,ofl. given .-absolute valuarep;

resentsagreater percentage variation. than in thecase of heavy. gauge-sheet or; strip.- In .addiatiom variationiin thickness due to: uneven an.--- neali-ngis to some extent cumulative overraeseries of .anneals and reductions in thickness by rolling; unlessconsi-derablecare is:exercised:-to maintain even thickness during; each. rolling, operation:

In..e xtr eme. casea: thicknesst variations. as great as .-0.@08-. inch in. rolled strip nominally 0.030% inch in ,th-ick-ness have-beeninoted. This corresponds to. a... thickness variation,- amounting to.v over 25. per cent of,the..nominaltthicknessl.

Heretofore theskill, of, the. man. performing, the rolling operations.v has been..a..major. factor in coping: withthisiproblemn The roller mane ually' endeavors. tocontinuously. adjust the. roll;

ing'"'pressure' as the strip passes between the rolls to maintain even" thickness of the rolled product;- A high degree of skill isnecessary to accomplish this successfully.

Various types 'of-continuously indicating thicknessgauges have been-developed to provide visual indication of the thickness ofthe' strip emerging from the rolls; These instruments" have been of substantial benefit in helping to maintain the strip" within commercial thickness tolerances but they havenot eliminated the problem nor appreciably'reduced the skill required onthe part of the roller.

Various'efforts have been'made to devise automatic means for controlling. the rolling pressure in response'to thickness indications given by'a continuously acting. thickness measuring instrument. So far as we are aware, however, these automatic controls havenever been applied successfully to the rolling of copperand copper alloys. We attribute this lack of success to the tendency of automatic controls to hunt, that is, to. cause the rollingpressure to oscillate above and below the value thatshould be maintained. In. extreme cases, .this.hunting..effct may be so I seriousas actual1y-to resultlin.a'rolledstrip of even more varying thickness thanif'nocontrol is employed.

The present invention provides an improved apparatus for automatically controlling the rolling pressure exerted by a rolling ,mill inresponse to thickness.variationsinthe rolled sheet. The invention. contemplates. provision. for minimizing the.efiectoffiovervcontrol and hunting, so that rolled. sheet or stripmaybe producedwithin very close. thickness. tolerances.

Inaccordance with the invention, the. extent to which. the thickness of the sheet emerging from. the rolls varies from. a desired standard thickness .is measured by means which produce electrical currents. of. intensity related in mag nitude to the magnitude of such variations. Thesecurrents are utilizedas-control currents forrautomatically adjusting the rolling pressure,

but the control action of the currents is re--- peatedly interruptedso as. tominimize overcontrol andhuntingand so to maintain the .by 'gauging means which produce anelectric current of. magnitude. related to the. thickness of the metalemergingtrom the rolls- A. repeating timer repeatedly interrupts the output of the relay, hunting.

In one" advantageous embodiment of the inthereby minimizing over-control and vention, the output current from the gauging means operates a galvanometer carrying a, mirror, or other device, for directing a beam of light back and forth between a pair of photoelectric cells. The output currents of the photoelectric cells actuate relays, which in turn actuate, through the repeating timer, the motors or other means by which the rolling pressure is controlled. The thickness tolerance to be maintained is set by appropriately adjusting the spacing between these photoelectric cells.

In a further embodiment of the invention, a second pair of photoelectric cells is arranged so as to be energized by the light beam in case the thickness of the rolled sheet departs materially from the preselected tolerance initially established. These additional photoelectric cells are arranged to cut out the repeating timer and so cause the rolling pressure to be changed rapidly to restore the thickness of the rolled sheet to within the desired tolerance.

The invention will be better understood from the following description of a specific embodiment shown in the accompanying drawings, in which Fig. 1 is a diagrammatic representation of the new control;

Fig. 2 is an elevation of a form of mount for the photoelectric cells;

Fig. 3 is a plan of the mount shown in Fig. 2; and

Fig. 4 shows in perspective the cam represented in Fig. 1.

In Fig. 1, a rolling mill comprising rolls (only the upper roll H3 is shown) mounted between roll frames H is diagrammatically illustrated. The rolling mill is schematically shown as provided with screw-down motors i2 and l3, each driving a shaft I l through which roll screwdowns l5 are operated. The first motor 52 rotates in a direction to bring the rolls closer together, and the other motor I3 rotates in the opposite direction to separate the rolls.

A strip of metal i6 is shown passing through the rolls. The thickness of the strip as it emerges from the rolls is measured by a continuously acting measuring instrument, such as a flying micrometer, having rollers (only one roller I! is shown) bearing against opposite sides of the sheet. The rollers H are urged toward one another against the sheet by spring means and so are always separated by a distance equal to the thickness of the sheet passing between them. If the sheet is of varying thickness, there will be slight movement of the rollers toward and away from each other. A minute electrical current of magnitude related to and measured by the spacing of the rollers, and hence to the thickness of the sheet, is produced in the micrometer head l8. This head is electrically connected to an amplifier unit 20, and the amplified current registers on a microammeter 2|. The current registered by the microammeter is proportional to, or otherwise a function of, the thickness of the sheet passing between the rollers H, and hence the microammeter reading indicates the thickness of the strip. One form of thickness measuring instrument of this character which may be used in accordance with the invention is the Electrolimit continuous thickness gauge, Model D, manufactured by Pratt 8; Whitney Company, of Hartford, Connecticut. It is understood, however, that this particular gauge is named only by way of example, and that any thickness measuring instrument which produces an electrical current related in magnitude to the thickness of the sheet being measured may be used.

A moving-coil galvanometer 22 carrying a mirror 23 is connected to the terminals of the microammeter 2!. A light source 2t connected to a power supply line 25 projects a beam of light against the mirror 23. As the coil of the galvanometer moves back and forth in response to changes in the magnitude of the current supplied to it through its connection to the microammeter, the light beam reflected by the mirror 23 is defiected from its normal, central position and moves back and forth between two photoelectric cells 25 and 2'3. These photoelectric cells are connected respectively to photoelectric relay units 28 and. 30. Each of relay units includes an amplifier circuit for magnifying the current which passes between the electrodes of the photoelectric cells when they are illuminated sufficiently to actuate relay switches 3i and 32 in the respective relay units 28 and 35. Various types of photoelectric relay units, such, for example, as the Photoelectric Relay Unit Catalogue No. CR7505-K108 G12, manufactured by the General Electric Company, of Schenectady, New York, are available for use in our control equipment. This particular relay is mentioned only by Way of example, as any suitable relay may be used.

One terminal of each of the relay switches 3i and 32 is connected to a terminal of a timing switch 33 forming a part of a repeating timer 34. The repeating timer also comprises a timing cam 35 rotated by a motor 38 which is connected to the power supply line 25. The switch 33 is of the normally closed type, but may be opened by depressing a plunger 3i. A lever as bearing on the plunger 3'? and also on the timing cam 35 causes the plunger to be alternately depressed and released as the timing cam rotates and alternately raises and lowers the lever 38. The timing mechanism thus serves repeatedly to open and close the circuit through the switch 33.

The timing cam 35 advantageously is of the type consisting of two or more similar cam wheels 60, 6| (Fig. 4) which may be adjusted angularly with respect to one another and then may be clamped together on the drive shaft 62 by locknut 63. This angular adjustment of two or more cam Wheels changes the length of the cam surface and permits adjusting the proportion of the time the lever 38 is depressed (or released) out of each full cycle of its motion, viz., per interruption cycle. Several pairs of cams may be provided so that various ranges of timing may be obtained.

The rate at which the timing cam should make and break the circuit through the switch 33 depends on many factors such as size of the rolling mill and electrical characteristics of the screwdown motors, but in general the full cycle of make and break should be of the order of one second or less time in length.

The timer shown in the drawings and described above is a mechanical timer and is entirely satisfactory for use in accordance with the invention. However, electronic timers, such as a pair of type 'Il5U Cycle Timers, manufactured by Photoswitch, Inc., of Cambridge, Massachusetts, may be used equally well. The particular form of timer employed is optional so far as the present invention is concerned, so long as it is capable of repeatedly and continuously interrupting the control circuit in which it is connected, independammo??? inflfiencedsbyz: thezscrew-dcmn motors; or): W the contmiithereofi .or by the:rotationxoryrateeof roetation ot rthetrollss;

- Theeterminal: o'tithestimingaswitchfiii opposite? that; toczwhioh .the relaya'switchessfilrandzz32 are; connected, .is; connectedito; one: (upper); side; of; thersupplyglineefin. Thezterminalcokthe firstrlree switch: 31: opposites that: connectedu to: the: timerrisnconnected; to: one: terminaliof .th'e: first: screwedowrr; mctorzz- 1.2;... and: thes other: terminaL theemotot: ccnnected'atocthe: other; (lower); sifieoifrtheesupplyrlimxfie. Similarly; ,aiterminal ofirthezsecondirelay.switchefliis connectedgto: one tcrmina'lofrtheisecondscrewedowrrmotor:i 3i; and". .thczctherztermzinai ofwthis motorsalsmisconnected: tmthersuprpiyclines 25L Thusrtheefirsttmotor; l2; thrcuglriwhiclt. the; rolls; of the. rolling brought closer togethemisccormecizciacross; thee supplyvlirle: 25: through: the-first; relayr switch 3 i and thestimingeswitch: 3132;: and thezsecondymotoi wetlnou ltwhichrtheerolls areeseparatedis cone nested: acrosszthe; supply line thronghzthe;secorral; rclawswitChQ-Z: and thevtimhrgzswitchtt:

S0 along assthethickness:of-tliesstripzbeing:trolled: issvcithin $hBSD1'fiSB1EBfaQdZtOiBIBHIQBL-(Whifih'.iSTdLEltermincd hysthe aphysical,;.spacing .cr the; photonelfll'sric:Ce11fi2251an15h21).;. the current; supplied-1m: thee galvanometers: 22- is? off such; magnitudeixthat thestlightibeamzzrcflected hyithe: mirror szt 'OSCflr' latesshetweenithephotoelectric :cc11s7.btlt :doesmct: fall upon eithermoflthemi Thesexcel'lsathercforez are not actuated, the relay switches ;,3i:a nd3 32 remairrnopenhandithez motors: lizraneh 53;. do. not operate: Consequentlwtlie spacinccand pressure: betweenrtherrollszofigthe rolling-mill remain ,essene I tiallsc; constant, If; however,, as hard; section; occursi the; strip; and: the thickness, of: the; emerging; strinr: increases. beyondihe preselected: tolerance, thecnrrenteimout to thergalva-ncmeteri- 2:2, isnhanged.snfliciently tn'deflectthe moving-coil and mirror enough to. reflect theeh-ght-beammnto theeactivesurface otthe-first photoelectric: 062L325; which in turn-actuatesthe relay uni-t 32 fletoeitectclosing? ct :theswitch .34 As'rairesul-tthe motor. [leis-operated toibringthe-erollsiot ztheerollin-g mill closer together. andincreaseithe rolling pressure; during 7 the. intervalstthatsthe: timing. switch: 33+ is;- closed. With; the :relay. switch. It! closed the. efiect-nfithetiming switch is, t0..permit .a..series.o:f current pnlsesaather; than a, steedycurrent-flowr to.passthroughthemoton L21; thus causing. ilk-150: operate. interruptedlyi. This interrupted opera.- tionof. thelmotonenablesjt. torincreasertheerolling pressureby increments .03: the. amount wreouired withounoyerincreasing and z so. minimizes, any, tendency tcwardlover-contrctand hunting.

Ina. similar... fashion, the emerging strip.

shouldhe. ofladthicknesslbelcw the. desireclitolerr once, thetgalyancmeterl2.2;,is deflected ill'thfi-fip; nositehdirection and ,thedieht. heamis refiected .on. to: .the activesurfhceoi,the.secondrphot'oelectricw celLjZlL The-relay.switchjh.therenpon...isuclocedi ancLthc motor. 1 his. operatedthrough.thleetimingn switch. 33 toi decrease :the' rolling; pressure.

Occasionally,- .beca11se of..an..exceptiona1ly, hard; section inthe, strip, being, rolled, on for, some. other reason, the thickness of the emerging-strip. may, depart. substantially, fi0m the preselected tolerance limits. If. this. occurs,. the appropriate. screw-dowmmotor l2or ltjshould be operatedf rapidly t0 compensate for, this extreme thick-- oihouter:photoelectric:cellsiflzhnd e iima gheeprce= vided: Eachzof TEHBSEEQIiOtQGlGCfiIiOZ081155515 5001152 neetedztcaaiphotoelectriczrelay:unit:Azaincludingt anramplifierrand arrelayswitch 43;; Thisswitch 4.3:is. connectedi'across theatermina-lsof "theztime in'gz-switch 3.3;: so that whemthetswitchrfl 715 .closed: the timing switch aisi-short circuited': Theaouter: photoelectricccel'lssdiliand 4 czareesomewhat more] widely separated than :the: inner: pair: ofqphotce 1 electric cells 26 and 21, and light reflected:fromiv the; mirror: 23; falls; upon: them; only, when. the galvanometer; is: deflected: beyond: the: limits; throughzwhichitnormally-oscillates; Theroutericellssdilnand .41, hOWGYeI,. arezlocatedawith respect. tottheiinner:cel1s-.-2Band*2l so that when .the reefiectedzbeamxotrlightafallsmponeither; of these. outerzcel'lstdteoncl; italso will fall upon the act-- jacent :inner: cell 25mm 211 If the thicknessiofithezemergi n as s? enough: so: that :thegaivancmeten 22;- is deflected to; the: point; where light; is. reflected I from the; mirror? 2 3 on". to; the iactivezsurface of {then outeri photoelectric eel-1141!; thez'result is thatzbothmfz thecphctcelectrio cells .26 and 49 4 are activated; and both. of the relay; switches '31 3 and 43 are,- closed;:. The; circuit. through the motor; l 2,-1is; thereby completed; as the timing switch 3311s; shorted. outbyx'the :closed relayrswitchjt, and the;- motor; 12 operateswithout interruption .until the. rolling :pressure; has; increasedsuflicientlm to; reduceethe thickness-bf: the; emerging strip torae value; within: the tolerance-v range: in; which. no light is; reflectedzonctoa the-"photocell 40. When: the: photocell flfliis: noelonger :activated, the relay switch. 43.; opens and the '.-timing;-switch-. is'iiagaim efiective;fen-interrupting the: circuit in which-zit: is-connected.

Irr;-a;-.similar--manner; ifithersthicknessr of sheet-decreasesmuch below therapreselected toler.+= ance;; the galvanometer: 22 is deflected enough: so that light-reflected. from, theymirror- 231 line pingees on the: outer photoelectricccell? M .asewell. assorr its: adjacent inner photoelectric,cellj l. Hares-again; the relay; switch; 4-3 =isiiclosed,z.short=- ing out: the; timing; switchn33; and; the; circuit: through the motor I 3 that is closed in 0011.88?" qnencexot closurewofrtheerelay switch. 32; The motor I 3 therefore; operates rapidly? withouttine terru-ptiontor reduce, the rolling: pressure; until? the thickness ofthewemergingr stripghascihcreased: to. within 1 the preselected tolerance; limits;

It: is.- apparent: fromv. thee foregoing: that the physical spacing of the photoelectric: 081151 26rand 21. determines the: thicknessntolerancea that": will normally; he maiisltain'ed5;thecontrol heres in described: Diflierent tolerance-limits are --.com-- mercially establishectfor diifierent metalsi and for difiierent'. thicknesses;- Widths; and-rgradescoffthe": some metal. AccordinglwweLcontemplatesmmmt ing theephctoelectriczz 06115250 thatthe spacing between them may; be; readily: adjusted by control: means to correspond? to: whatever thick nessz: tolerance;- is}; to beimaintainediz; A suitable mounting; of; this: character-r. is: shown-' in: Figs: 2 andr3. The mounting. unite-shown comprises a; pair-.1 of upright ZSi'ETBITBaTI-TBSLQ 5:? fastened by angle ironse lfimn-othei :suitablezmeansz to a,-base' board 41,. A'spaced pain-of.rodsa llhextends' betweenthe two-:side frames; A:pair;:ofiiturb'escarriages ml aresupported. on the: rodsr 48'='- by: grooved rolls 5!.

1 1185110615 thusprovide1waysialongswhichsthe carriagest 5% may be :moved-towardw or away from eachother. A.sprocketchaintfim'passes around" a pairotsprocketwheels .53ianda54, oneroi which';

mess. variation; Edr; thi. p l p e.,a.secondfpfl .75.is-.m0unted;.orreachlsideframey Theiuppecloom of the sprocket chain 52 is connected by a screw 55 to one of the carriages 50, and the other loop of the sprocket chain is connected by a screw 56 to the other carriage. One of the sprocket wheels 54 is provided with a crank handle 51 for conveniently turning it. As the crank handle is turned clockwise, the carriages 50 are moved toward each other, and as it is turned counterclockwise, the carriages are moved away from each other.

' On each carriage 50 is mounted a tube support bracket 58, on which sockets 59 for the photoelectric cells are fastened. The photoelectric cells 26, 21, 40 and 4| are mounted in these sockets. As shown in the drawings, it is advantageous to configure the tube supporting brackets 58 so that light reflected from the galvanometer mirror 23 impinges on the cells substantially perpendicularly to their longitudinal axes.

- The particular form of mount shown in Fig. 3 is designed for use of physically large photoelectric cells 26 and 21 for main control purposes, and physically small photoelectric cells 40 and ll for shorting out the timer. It is evident, however, that four photoelectric cells all of the same physical size may be employed by suitably changing the shape of the brackets 58, or by mounting the sockets for the main control photoelectric cells 25 and Z1 relatively farther out from the surface of the brackets than the sockets for the other pair of photoelectric cells.

By turning the crank 5'! and thus moving the carriages 50 toward oraway from each other, the photoelectric cells may be spaced apart any desired distance within the limits of travel of the carriages 50. The tube mounting structure described above may be calibrated in conjunction with the sheet metal thickness measuring instrument employed, and such calibration may be noted by markings indicating the position of the carriages 5!). After such calibration, it is a simple matter to set the photoelectric cells at a distance apart corresponding to whatever thickness tolerance it is desired to maintain in rolling sheet metal in a rolling mill equipped with the new control.

We have found the control herein described to be highly effective in maintaining very close thickness tolerances in rolling non-ferrous alloy strip to thin gauges. have maintained automatically in accordance with the invention are very much closer than standard commercial tolerances for sheet metal, and in fact are very much closer than can be maintained commercially either manually or by controls heretofore proposed or available.

' It is understood that the invention is not confined to the embodiments specifically described herein in conjunction with the drawings. For example, it is not necessary that two separate motors be employed to operate the roll screwdowns. .It is equally possible to use a single re versible motor, and connect the relays so that actuation of one relay causes the motor to operate in one direction to bring the rolls closer together and actuation of the other relay operates the motor in the opposite direction to separate the rolls. Or two reversible motors may be used, one operating on each side of the rolls, so that either side may be screwed down or up independ used. The use of reversible motors to control roll screw-downs is common practice in the art.

Similarly, it is not necessary to employ a measuring instrument which actually bears against the metal emerging from the rolls. Measuring instruments including elements between which the strip passes without actually coming in contact with them are available and may be used equally as well as an instrument of the type particularly described herein. For example, gauging means using X-rays to compare the thickness of the rolled strip with that of a standard specimen, and having an electric current output related in magnitude to the difference in thickness between the rolled strip and the specimen, are available and may be used successfully. It is only necessary that the thickness gauging instrument and its associated elements have a current output which is related in magnitude to the desired thickness of the strip and is therefore capable of serving as an initial control current.

Particular reference has been made herein to gauging instruments that produce a current re lated in magnitude to the thickness of the sheet,

' but instruments that produce a, voltage, rather than a current, so related to the sheet thickness may be used equally well. In stating that the gauging instrument produces a current (or voltage) related in magnitude to the sheet thickness, it is understood that the instrument may actually generate such current (or voltage), or it may simply modify a current or voltage supplied from an external source so that the magnitude thereof becomes related to the sheet thickness.

We claim:

1. In apparatus for rolling sheet metal comprising a set of rolls, electrically operated pressure adjusting means for adjusting the pressure between said rolls, and gauging means producing electrical currents of magnitude related to the thickness of sheet metal emerging from the rolls, the improvement which comprises a pair of spaced photoelectric cells, a light source, optical means for deflecting a beam of light from the source from a, normal line to one of said cells whenever the current produced by said gauging means corresponds to sheet thickness below the desired tolerance and to the other of said cells whenever such current corresponds to sheet The tolerances which we thickness above the desired tolerance, a relay connected to the first photoelectric cell and actuating the pressure adjusting means to decrease the rolling pressure when light from the source is directed to said first cell, a second relay connected to the second photoelectric cell and actuating the pressure adjusting means to increase the rolling pressure when light from the source is directed to said second cell, repeating timer means for repeatedly and continuously interrupting actuation by the relays of the pressure adjusting means, and means independent of the electrically operated pressure adjusting means, and independent of the operation of said set of rolls for continuously operating said repeating timer means to minimize overcontroll and hunting, and means for adjusting the spacing of said photoelectric cells from said normal line, whereby to efiect the adjustment of the sheet thickness tolerance which is to be automatically maintained.

2. In apparatus for rolling sheet metal comprising a set of rolls, electrically operated pressure adjusting means for adjusting the pressure between said rolls, and gauging means producing electrical currents of magnitude related to the ofzovercont-rol andhuntingcofasaidmressnrewad- -justing.:means. I

,3; 'In ;..apparatusgfor:rollingcsheemmetal comprising fa:lSet'lOf' rouse-electrically: .=op.erated vpresisureiadjustingrmeans for eadiusting thecpressure between said ."roljls,- a'upoivensourcei for energiz- 1 ing said pressure,adjustingrzmeans and; gauging imeans producing electrical i,,;currents ofnmagnitude related v.to sthe i thickness of sheet :metal emerging from the rolls, the improvement. which comprises :a: pair of spacedcphotoelectriccellsaa light -sou=1ce, =rmeansflforidirecting 'lightitfromanthe source to one er -the other 'of saidacells to energize the same whenever the :current produced E-byLsa-id :gaugi'ng -means corresponds to sheet thickness cutsideapreselected tolerance, relay means actuated in response to said photoelectric c'e'lls and connected to said powersourceandto: said pressure adjusting-means for iactuating sa-id i ipressure adj-usting means'in response toaenergization ot the "photoelectric cellseas required to :maintain the thickness of the rolled 'sheet metal: substantially Within the preselected tolerance, and --means operatingindependently of :said pressure adjustingmeans and independently of the op- *eration of saidset" of I rolls for =repeatedly-and continuously interrupting the actuation by: said relaymeans of --said pressure: adjusting means-to minimize .overcontrob and hunting thereof.

4. I-n apparatus F for rolling sheet metal= com- "prising a set of rolls-electrically operated pressure adjusting means for adjusting the pressure between said roll-s; and gau'ging' means :producing electrical currents of -magnitude related -to the thickness of sheet-metal-emergi-ng from the-rolls, the in'lprcvement whichcomprises first-phot'o- --e1ectric *means connected tocontr'ol the actuation of-said pressureadjusting means in response to the currents produced by said gauging-means as required to mainta-in thicknesspfthe rolled-sheet substantially -withina preselected tolerance, re- "peat-ing timermeans connected to said pressure adjusting means and disposed to repeatedly interrupt the energization of the pressure adjusting means so -'--as to' minimize over-control and hunting-and second photoelectric means responsive to currents produced by said gauging meansrzoffimagnitudecgreater than that of 5;the first-named currents, for cutting out the effect of said repeating timer meanssoas to operate saidipressure adjusting means continuously'whenrever thickness oithe roll d sh e partssu stantiallywfrom Within the, nreselectedutclerance. 25.111 app ratus forrollin a'she t metal compri ing a :setoof rolls, electrically; operatedszpresisureoadjusting means. foradius-ting thespressure betwcen said rolls,..and gauging :means prod cing -IeIectrical' currents of magnitude: relatedstoithe thickness of sheet metal emerging from the r dlls, "the improvement which comprises a pair of spaced photoelectric cells, a pair of mounts mov- :able toward andiawa-yi eac zcthenonrwhich flfiaild izcells ;are :supported, mean vfer ad ustin th escaein cor .qsaid moun s and az-thus "cf said tphotcelectniccells, iwith-sresnect eachu therct 5 andistancerieorresnemlinatc arpreselected sheet thickness tolerance which it is desiredyto'maintainca diehtisonrce; means for directin lie ht fremcthezscurc fiflzfil'lexmcthfil thencfssaidrcells atoienereizezther amezwhenerertheacurrentrpro- 1 :idnced iiby isaid g using means :COIIGSQQI'IGS c-to tsheetathickness@outside a :pres'elected tolerance, relayzcneansgconnected,., oasaidrphotoelectric 3cetlaandiactnairing;eaimpressure"adiustingrmeans unrespanse atmaenergization :of the photoelectric icells vwas i-reeuired 1 to ,ma-intam the nthi'ckness 10f the rolled csheetametal substantially 'iwithin :the

snreselected'itclerance.

6121 Inza-pparatus for: rolling. sheetumetal qcomprisingpasetzof rollspelectrically .operatedapres- --surezadiustingimeansion adjusting the -;pressure ebetween saidmolls;andigauging; means; producing electrical; currents iof magnitude ,-rela-.ted =1to Ibh athickness iofxsheet metal emerging fromv the, rolls, the improvement which comprises, a pair =.of

spacediphotoelectricccells,at light source, means -iorr directing=ian iundeflectedi beamzof: light from thesourceia-longia :ncrmal line, meansfor'deflectring said :beam: to impinge eon.arfirsttofrsaidenells awheneversthe currentnproducednby .saidegauging "means;@correspondsi'to sheet thicknessbelow-'ithe 1 desired: tolerance; andxtowimpingeon :arisecond 10f zisaidacells'iwheneizerrsaid currentworresponds-to ssheet thickness above 1 the desired ztolerance, ha .relay;connectedtohexactuated Joy thefirst-photoelcctriccelhandiconnectedto actuatethe pressure zadjustingwmeansvto decrease'1the= rollingapressure zzwhenlirlight xtheasource impinges won :said firstlcell and-a:secondirelayiconnectecl to beiactuatednebyctheasecond .xphotoelectric cell. and con- 4 merited itoe. actuatexthe. pressure adjusting. means xto increaSexthe rolling pressurciwhenlightffrom attic-sourceisidirecteditosaidsecondicell,repeating --timermeans connected in the output circuits of said-:relay'forrepeatedly interruptingactuationiby a, the relays .iof the:';pressure 1 adjusting; means -;.to "minimizei-ioyerrcontrol e and hunting thereof, ea secondxpa-inof photoelectric .cellscomprising andpfourthi cells spaced furtherifromsaidwnormal 1linejthanvarezsaidifirstrand :second cells,-;respectiiljely, izbnlihz of= said: :pairs; ofwcells ubeing 080355.8-

posed with respect to said light source that-ia small deflection of: said ilight source from. :said normal ilinezactivates ion-1y the-"first or: second cell eof isaid" first main :of cells andra :larger idefiection :thereofuactivates ':b0l7h=:Said first andthirdcells, 'only,- ora-said: second :and ,zfourth cel1s,a on1y,.:and gatiihird;512,5 7 COIIDBClJfidZlZOLZbG .=ac.tuated byusaid zthirdzand iounthmhotoelectric;cells and connected ztothearepeatingtimenmeans-i h 1 la xi actuated,- wherebyzthe z'fiffectnof :said repeating ,ztimerameans isalcut,aoutaezwhenever: the: thickness cfntherrclledzsheet.:denarts:sufiicientlyerrcmi."the

cpiieselected wtolerance 115.0 athat alight a from said 651QUTCB1SIdil'fifit edttafimpingeiQn either said third -er fourth cphotoeleotricecell, land wherebyu-ithe reflect of:=.-saidvrepeating itimeri means is :cut :in

--again When-"the thickness. ofisaid rolledxsheet closelypapproachessaid tolerance.

37 .i mnzapparatus according: .to claim 6, -:a-iriairnf @carriages :morahle-rtowardaand away from; each 5.0131161, esaid :afirst and third nphotoelectrici cells being:mounted-iomoneaofi said carriages ,andisaid -eeccnd sand iourth zxphotoelectric scells aibeing mounted on the other of said carriages, and unicontrol means for simultaneously moving said carriages toward and away from each other to the same extent so as to adjust the spacing between said first and second cells, respectively, and between said third and fourth cells, respectively.

8. In a mill for rollin sheet metal which includes rolling pressure means and means for continuously determining the extent to which the thickness of the sheet emerging from the rolls varies from a desired standard thickness, the improvement which comprises means for producing, in response to variations in thickness of the sheet, electrical current of intensity related in magnitude to the magnitude of the variations, means for controlling the adjustment of the rolling pressure in accordance with variations in intensity of said current, and means indedependent of the adjustment of said rolling pressure for repeatedly and continuously interrupting the control action of said current at a rate independent of the operation of said rolls, thereby to minimize overcontrol and hunting and to maintain the thickness of the rolled sheet substantially uniform within preselected limits.

9. In a mill for rolling sheet metal which includes rolling pressure means and means for continuously determining the extent to which the thickness of the sheet emerging from the rolls varies from a desired standard thickness, the improvement which comprises means for producing, in response to variations in thickness of the sheet, electrical currents of intensity related in magnitude to the magnitude of the variations, electric means for controllingthe rolling pressure, means for controlling the adjustment of said electric means in accordance with variations in intensity of said current including electric contacts connected to actuate and deactuate said electric means by repeatedly and continuously interrupting the control action of said current at a rate independent of said adjustment of the rolling pressure and independent of the operation of said rolls, thereby to minimize overcontrol and hunting and to maintain the thickness of the rolled sheet substantially uniformly within preselected limits, and means operable independently of the means which controls the adjustment of the rolls for adjusting the ratio of open to closed periods of said contacts per interruption cycle.

10. In apparatus for rolling sheet metal comprising a set of rolls, electrically operated pressure adjusting means for adjusting the pressure between said rolls, an electrical power source for operatin said means, and gauging means producing electrical currents of magnitude related to the thickness of sheet metal emerging from the rolls, the improvement which comprises, light deflecting means operable in response to said electrical currents, first and second photoelectric means actuated in response to light from said light deflecting means, relay means, connections between said first photoelectric means and said relay means, and between said relay means, said power source and said pressure adjusting means through which actuation of said pressure adjusting means is controlled in response to the currents produced by said gauging means as required to maintain thickness of the rolled sheet substantially within a preselected tolerance, repeating timer means operated independently of operation of said rolls and including circuit-interrupting means connected between said power source and "said pressure adjusting means operable'to repeatedly interrupt the power to said pressure adjusting means so as to minimize over-control and huntin thereof, and switching means responsive to said second photoelectric means connected to cut out the circuit-interrupting effect of said circuitinterrupting means so as to operate said pressure adjusting means continuously whenever the thickness of the rolled sheet departs substantially from said preselected tolerance.

11. In apparatus for rolling sheet metal comprising a set of rolls, electrically operated pressure adjusting means for adjusting the pressure between said rolls, gauging means producing electrical current of magnitude related to the thickness of sheet metal emerging from said rolls, a relay having an output circuit connected to control the operation of said pressure adjusting means, and means for actuating said relay in response to a predetermined magnitude of current produced by said gauging means and in such manner that the pressure adjusting means is operated to change the rolling pressure as required to maintain the thickness of the rolled sheet substantially uniform, the improvement which comprises means independent of said pressure adjusting means for repeatedly and continuously interrupting the output of said relay at a constant rate which is independent of the pressure adjustment of the rolls, and means responsive to current of magnitude different from said predetermined magnitude, independent of the electrically operated pressure adjusting means and independent of the operation of the rolls for annulling the interruptions of the output of said relay.

12. In a mill for rolling sheet metal which includes rolling pressure means and means for continuously determining the extent to which the thickness of the sheet emerging from the rolls varies from a desired standard thickness, the improvement which comprises means for producing, in response to variations in thickness of the sheet, electrical current of intensity related in magnitude to the magnitude of the variations, means for controlling the adjustment of the rolling pressure in accordance with variations in intensity of said current, and means independent of the adjustment of said rolling pressure for repeatedly and continuously interrupting the control action of said current at a rate independent of the operation of said rolls, said rate being of the order of one second or less per interruption cycle, thereby to minimize overcontrol and hunting and to maintain the thickness of the rolled sheet substantially uniform within preselected limits.

WILLIAM R. MACAULAY.

JOHN E. COOLIDGE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,818,103 Sperry Aug. 11, 1931 1,969,536 Winne Aug. 7, 1934 2,114,603 McBain Apr. 19, 1938 2,259,323 Peterman Oct. 14, 1941 2,264,095 Mohler Nov. 25, 1941 2,275,509 Dahlstrom Mar. 10, 1942 2,279,579 McElhinney Apr, 14, 1942 2,332,289 Zeitlin Oct. 19, 1943 2,356,579 Gardner Aug. 22, 1944 

